1. Field of the Invention
This invention relates generally to controlling vehicle driveline torque, particularly through engine output torque delivery during high demand operating conditions, which should occur infrequently in the life of a vehicle, while limiting torque to protect driveline components from fatigue type failures during more normal operation.
2. Description of the Prior Art
Vehicle driveline components, such as transmissions, driveshaft, axles, etc., have a finite fatigue life when subjected to input torque loads during the life of the vehicle. Empirical data is often used to establish a relation between the magnitude of the torque load and the number of applied cyclic applications of that load before fatigue failure of the tested component occurs.
To ensure an acceptable length of service life of the component under normal use, torque limitations may be applied to prevent the application of high magnitudes of torsional loading on a regular, recurring basis. Because such high magnitudes of torque are lower than the ultimate strength and yield strength limits of the component, a limited number of cycles at high torque magnitudes would not have a substantial adverse affect on the component's fatigue strength.
A need exists in the field of vehicle driveline control for a strategy that permits application of higher magnitudes of torque in certain non-typical conditions, yet excludes such torque magnitudes during regular use when larger numbers of cycle occur.